Messaging systems are ordinarily designed to operate with a given modulation format. Personal messaging units (PMU's) or subscriber units that operate on the messaging system are designed to operate with this given modulation format. Very often a second, even neighboring, messaging system including it's corresponding PMUs will operate with or on a different modulation format. Because of the distinct modulation formats PMUs from these two systems will not be able interoperate on either system or operate on the neighboring system.
One solution that has been proposed is the adoption of an open architecture modulation format and protocol. If this were adopted by all messaging systems PMUs could interoperate on any system, subject to certain administrative formalities. Thus one open architecture modulation format could be utilized for all regional based messaging systems or effectively one wide area messaging systems. Various reasons such as the fast and ever changing user needs and telecommunications technology necessitating more capable modulation formats or the need to grandfather or accommodate existing formats have resulted in many practical obstacles to the wide scale success of standard modulation formats.
Additionally the advent of two-way messaging systems employing a forward or "outbound" radio frequency channel for message delivery to the PMU's or subscriber units and a reverse or "in-bound" channel for acknowledgments or the like has created even greater opportunity, if not necessity, for modulation format differences. The modulation formats may vary, justifiably, between forward and reverse channels or between data, voice, video or a combination of such messaging services.
In addition, some system operators have one way systems and were unable to obtain licenses for an inbound frequency that would allow them to offer two way services. These operators are driven to provide two way services, such as delivery guarantees and the like, using spectrum for the inbound channel from common spectrum allocations such as the ISM band of frequencies. The ISM band has been authorized by the Federal Communications Commission for general use so long as certain rules, such as power level limits, are followed and proscribed modulation formats are followed. Similar spectral authorizations are available in many other countries.
At the same time the greater mobility of the general population virtually mandates that a given PMU operate on a plurality of messaging systems and this trend seems to be growing. Clearly a need exists for a messaging system and receiver that is adaptable to varying modulation formats and corresponding methods of so adapting.